/*
  ==============================================================================

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
   copyrightable work, you agree to the terms of the JUCE End User Licence
   Agreement, and all incorporated terms including the JUCE Privacy Policy and
   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-8-licence/
   JUCE Privacy Policy: https://juce.com/juce-privacy-policy
   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

   THE JUCE FRAMEWORK IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL
   WARRANTIES, WHETHER EXPRESSED OR IMPLIED, INCLUDING WARRANTY OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE DISCLAIMED.

  ==============================================================================
*/

namespace juce
{

BufferingAudioSource::BufferingAudioSource (PositionableAudioSource* s,
                                            TimeSliceThread& thread,
                                            bool deleteSourceWhenDeleted,
                                            int bufferSizeSamples,
                                            int numChannels,
                                            bool prefillBufferOnPrepareToPlay)
    : source (s, deleteSourceWhenDeleted),
      backgroundThread (thread),
      numberOfSamplesToBuffer (jmax (1024, bufferSizeSamples)),
      numberOfChannels (numChannels),
      prefillBuffer (prefillBufferOnPrepareToPlay)
{
    jassert (source != nullptr);

    jassert (numberOfSamplesToBuffer > 1024); // not much point using this class if you're
                                              //  not using a larger buffer..
}

BufferingAudioSource::~BufferingAudioSource()
{
    releaseResources();
}

//==============================================================================
void BufferingAudioSource::prepareToPlay (int samplesPerBlockExpected, double newSampleRate)
{
    auto bufferSizeNeeded = jmax (samplesPerBlockExpected * 2, numberOfSamplesToBuffer);

    if (! approximatelyEqual (newSampleRate, sampleRate)
         || bufferSizeNeeded != buffer.getNumSamples()
         || ! isPrepared)
    {
        backgroundThread.removeTimeSliceClient (this);

        isPrepared = true;
        sampleRate = newSampleRate;

        source->prepareToPlay (samplesPerBlockExpected, newSampleRate);

        buffer.setSize (numberOfChannels, bufferSizeNeeded);
        buffer.clear();

        const ScopedLock sl (bufferRangeLock);

        bufferValidStart = 0;
        bufferValidEnd = 0;

        backgroundThread.addTimeSliceClient (this);

        do
        {
            const ScopedUnlock ul (bufferRangeLock);

            backgroundThread.moveToFrontOfQueue (this);
            Thread::sleep (5);
        }
        while (prefillBuffer
         && (bufferValidEnd - bufferValidStart < jmin (((int) newSampleRate) / 4, buffer.getNumSamples() / 2)));
    }
}

void BufferingAudioSource::releaseResources()
{
    isPrepared = false;
    backgroundThread.removeTimeSliceClient (this);

    buffer.setSize (numberOfChannels, 0);

    // MSVC2017 seems to need this if statement to not generate a warning during linking.
    // As source is set in the constructor, there is no way that source could
    // ever equal this, but it seems to make MSVC2017 happy.
    if (source != this)
        source->releaseResources();
}

void BufferingAudioSource::getNextAudioBlock (const AudioSourceChannelInfo& info)
{
    const auto bufferRange = getValidBufferRange (info.numSamples);

    if (bufferRange.isEmpty())
    {
        // total cache miss
        info.clearActiveBufferRegion();
        return;
    }

    const auto validStart = bufferRange.getStart();
    const auto validEnd = bufferRange.getEnd();

    const ScopedLock sl (callbackLock);

    if (validStart > 0)
        info.buffer->clear (info.startSample, validStart);  // partial cache miss at start

    if (validEnd < info.numSamples)
        info.buffer->clear (info.startSample + validEnd,
                            info.numSamples - validEnd);    // partial cache miss at end

    if (validStart < validEnd)
    {
        for (int chan = jmin (numberOfChannels, info.buffer->getNumChannels()); --chan >= 0;)
        {
            jassert (buffer.getNumSamples() > 0);

            const auto startBufferIndex = (int) ((validStart + nextPlayPos) % buffer.getNumSamples());
            const auto endBufferIndex   = (int) ((validEnd + nextPlayPos)   % buffer.getNumSamples());

            if (startBufferIndex < endBufferIndex)
            {
                info.buffer->copyFrom (chan, info.startSample + validStart,
                                       buffer,
                                       chan, startBufferIndex,
                                       validEnd - validStart);
            }
            else
            {
                const auto initialSize = buffer.getNumSamples() - startBufferIndex;

                info.buffer->copyFrom (chan, info.startSample + validStart,
                                       buffer,
                                       chan, startBufferIndex,
                                       initialSize);

                info.buffer->copyFrom (chan, info.startSample + validStart + initialSize,
                                       buffer,
                                       chan, 0,
                                       (validEnd - validStart) - initialSize);
            }
        }
    }

    nextPlayPos += info.numSamples;
}

bool BufferingAudioSource::waitForNextAudioBlockReady (const AudioSourceChannelInfo& info, uint32 timeout)
{
    if (source == nullptr || source->getTotalLength() <= 0)
        return false;

    if ((nextPlayPos + info.numSamples < 0)
        || (! isLooping() && nextPlayPos > getTotalLength()))
        return true;

    const auto startTime = Time::getMillisecondCounter();
    auto now = startTime;

    auto elapsed = (now >= startTime ? now - startTime
                                     : (std::numeric_limits<uint32>::max() - startTime) + now);

    while (elapsed <= timeout)
    {
        const auto bufferRange = getValidBufferRange (info.numSamples);

        const auto validStart = bufferRange.getStart();
        const auto validEnd = bufferRange.getEnd();

        if (validStart <= 0
            && validStart < validEnd
            && validEnd >= info.numSamples)
        {
            return true;
        }

        if (elapsed < timeout
            && ! bufferReadyEvent.wait (static_cast<int> (timeout - elapsed)))
        {
            return false;
        }

        now = Time::getMillisecondCounter();
        elapsed = (now >= startTime ? now - startTime
                                    : (std::numeric_limits<uint32>::max() - startTime) + now);
    }

    return false;
}

int64 BufferingAudioSource::getNextReadPosition() const
{
    jassert (source->getTotalLength() > 0);
    const auto pos = nextPlayPos.load();

    return (source->isLooping() && nextPlayPos > 0)
                    ? pos % source->getTotalLength()
                    : pos;
}

void BufferingAudioSource::setNextReadPosition (int64 newPosition)
{
    const ScopedLock sl (bufferRangeLock);

    nextPlayPos = newPosition;
    backgroundThread.moveToFrontOfQueue (this);
}

Range<int> BufferingAudioSource::getValidBufferRange (int numSamples) const
{
    const ScopedLock sl (bufferRangeLock);

    const auto pos = nextPlayPos.load();

    return { (int) (jlimit (bufferValidStart, bufferValidEnd, pos) - pos),
             (int) (jlimit (bufferValidStart, bufferValidEnd, pos + numSamples) - pos) };
}

bool BufferingAudioSource::readNextBufferChunk()
{
    int64 newBVS, newBVE, sectionToReadStart, sectionToReadEnd;

    {
        const ScopedLock sl (bufferRangeLock);

        if (wasSourceLooping != isLooping())
        {
            wasSourceLooping = isLooping();
            bufferValidStart = 0;
            bufferValidEnd = 0;
        }

        newBVS = jmax ((int64) 0, nextPlayPos.load());
        newBVE = newBVS + buffer.getNumSamples() - 4;
        sectionToReadStart = 0;
        sectionToReadEnd = 0;

        constexpr int maxChunkSize = 2048;

        if (newBVS < bufferValidStart || newBVS >= bufferValidEnd)
        {
            newBVE = jmin (newBVE, newBVS + maxChunkSize);

            sectionToReadStart = newBVS;
            sectionToReadEnd = newBVE;

            bufferValidStart = 0;
            bufferValidEnd = 0;
        }
        else if (std::abs ((int) (newBVS - bufferValidStart)) > 512
                  || std::abs ((int) (newBVE - bufferValidEnd)) > 512)
        {
            newBVE = jmin (newBVE, bufferValidEnd + maxChunkSize);

            sectionToReadStart = bufferValidEnd;
            sectionToReadEnd = newBVE;

            bufferValidStart = newBVS;
            bufferValidEnd = jmin (bufferValidEnd, newBVE);
        }
    }

    if (sectionToReadStart == sectionToReadEnd)
        return false;

    jassert (buffer.getNumSamples() > 0);

    const auto bufferIndexStart = (int) (sectionToReadStart % buffer.getNumSamples());
    const auto bufferIndexEnd   = (int) (sectionToReadEnd   % buffer.getNumSamples());

    if (bufferIndexStart < bufferIndexEnd)
    {
        readBufferSection (sectionToReadStart,
                           (int) (sectionToReadEnd - sectionToReadStart),
                           bufferIndexStart);
    }
    else
    {
        const auto initialSize = buffer.getNumSamples() - bufferIndexStart;

        readBufferSection (sectionToReadStart,
                           initialSize,
                           bufferIndexStart);

        readBufferSection (sectionToReadStart + initialSize,
                           (int) (sectionToReadEnd - sectionToReadStart) - initialSize,
                           0);
    }

    {
        const ScopedLock sl2 (bufferRangeLock);

        bufferValidStart = newBVS;
        bufferValidEnd = newBVE;
    }

    bufferReadyEvent.signal();
    return true;
}

void BufferingAudioSource::readBufferSection (int64 start, int length, int bufferOffset)
{
    if (source->getNextReadPosition() != start)
        source->setNextReadPosition (start);

    AudioSourceChannelInfo info (&buffer, bufferOffset, length);

    const ScopedLock sl (callbackLock);
    source->getNextAudioBlock (info);
}

int BufferingAudioSource::useTimeSlice()
{
    return readNextBufferChunk() ? 1 : 100;
}

} // namespace juce
